We will attempt to map the chromosome of N. gonorrhoeae using a combination of procedures including marker frequency analysis, density transfer analysis and linkage analysis via cotransformation. The markers to be utilized in these studies include antibiotic-resistance, nutritional and ts markers already obtained as well as new markers which we will isolate after mutagenesis with ethyl methanesulfonate (EMS). We will continue experiments designed to define the mechanisms by which N. gonorrhoeae and Neisseria sp. in general limit the entry of and recombination with the DNAs of other species within this Genus. Our new studies will complement those already done with N. gonorrhoeae as a recipient for doubly heterologous hybrid donor DNA that specifies streptomycin resistance. In them we will utilize principally N. perflava, a species which we have found is more discriminating toward heterologous DNA than is N. gonorrhoeae, as the recipient for hybrid donor DNA. We also plan to expand our studies with N. gonorrhoeae as a recipient for doubly heterologous donor DNA to include transformation to nutritional independence. Heretofore our experiments have been limited to streptomycin resistance, a marker which is known to be conserved in most genera. BIBLIOGRAPHIC REFERENCES: Steinberg, V. I., E. J. Hart, J. Handley and I. D. Goldberg. 1976. Isolation and characterization of bacteriophage specific for Neisseria perflava. J. Clin. Microbiol. 4: 87-91. Goldberg, I. D. and V. I. Steinberg. 1977. Nutritional aspects of transformation and transfection. In: M. R. Rechicigl, Jr. (Ed.) Handbook of Nutrition and Food. CRC Press, Cleveland, Ohio (In press).